Captured German La-5 flight test

[HoHun]

Hi Tilt,

I just found the following quote in one of your old posts:

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Early La5 fns were fitted with only 3 of the 5 tanks fitted in the original La 5 this infact reduced range to circa 500Km..... with the advent of the metal sparred La5FN they introduced 4 tank set ups (2 x 168 L & 2 x 148 L) totalling 632 L . Air intake clutter at the wing roots and attempts to lighten the fuel load forced the La 7 back to 3 tanks ( 460/470 L).
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Since Lerche's La-5FN"V" had the 460 L tankage, does that help us to date it?

It seems it must either have been an early La-5FN with wooden wings then, or a very late La-5FN with the new La-7's wings.

The latter would fit the remark on armour thickness you made above.

Regards,

Henning (HoHun)

[minus]

Bogun , u can be wrong, in CSSR army we have to notice even each projectile ammo  for the service pesonal VZ 56 , like year of fabrication, and fabrication  batch serial  number,  for warfare that was 1000 % more strict, i know Rusian army was a very Bordelic system , what ever Soviet forces was  with us on shoting range on the poligon we always have to watch out , those soliers constantly lose something , like hand granade , ammo , even the AK 47,  what forst 1 soviet oficer even donot rememer where hi put hiz brand new ak 82

but last what i know about ,,high tech ,,  stuf in rusian army they was wery paranoid , and that before WW2 so if the first  planes showed up, i thing they kept serial traces  at last that time until  plane become outclased

[Tilt]

Originally posted by niklas
Never saw an original flight test document with detailded description.

first and last pages of 37 pages of original Russian flight test data on various la7's ............ stamped and signed.

They are scans of photocopies.......

I have them zipped in three files each of about 600kB...........

do you really want them or this this some kind of test?



.

[HoHun]

Hi Tilt,

>I have them zipped in three files each of about 600kB...........

Since I don't speak any Russian, that would be wasted bandwidth, but if there are any diagrams or tables that can be understood (with a bit of help :-), I'd be highly interested!

By the way, did you catch the bit about the fuel tank size? I had hoped you as our premier Lavochkin expert could use it as a help in dating Lerche's plane :-)

Regards,

Henning (HoHun)

[Tilt]

Originally posted by HoHun


By the way, did you catch the bit about the fuel tank size? I had hoped you as our premier Lavochkin expert could use it as a help in dating Lerche's plane :-)

Regards,

Henning (HoHun)

It does not help really...... I read recently that the Gorky plant produced so many wooden sparred wings in 43 for the La5FN. That whilst Moscow went onto metal sparred wings and subsequent la 7 production ... Gorky continued to produce la5Fn's with wooden wings up until October 44.

Hence Gorky produced the three tank la5Fn for some  months after Moscow plant had switched.

I have known that Gorky continued La5FN production due to its stock of wings...........I did not know (but do now from Yefim Gordons latest work) they were all wood wings.

On this basis the wooden winged 3 tank 460 litre La5fn was always the type produced at Gorky whilst Moscow (did) and Ulan Abe may have switched to the  4 tank prior to the production of the la7 coming on stream.

[HoHun]

Hi Tilt,

>Gorky continued to produce la5Fn's with wooden wings up until October 44.

Thanks, I had no idea it was so complicated :-)

Does the 460 L tank volume definitely mean Lerche's La-5 was a model with wooden wings?

Regards,

Henning (HoHun)

[Tilt]

Originally posted by HoHun

Does the 460 L tank volume definitely mean Lerche's La-5 was a model with wooden wings?

No not definately...........the best you could argue is a "most probably"....

and we still have a 50kg wheel base mis balance.

This could be due to some thing stupid like a deflated tyre and so the lower wheel bearing more load.........I just could not believe it.

It could be that the castor wheel was not in line or the prop weight not centralised when the ac was weighed...... seems a bit basic to miss.

It could be that one wing still has an old (out of use) outer tank in it...........equally implausable.

It could be that one wing is just plain heavier than the other.....(Gorky was infamous for "filling" gaps with resin to over come poor manufacturing tolerances) but 50Kg????

I am tempted to believe that it was a combination of some of the above...The La's did not carry out of axis components like the spit or the 109 (except for the pitot) and so should be balanced. Hence the prop not quite centre, the castor over to one side, a tyre slightly deflated, a little more glue etc.

[Siaf__csf]

The russians still today seem to be totally unaware of the rampant corruption, misinformation and abuse their whole system had (and partly still has.)

Any negative reports meant a trip to a gulag or even a shot in the back of the neck. The reports were surprisingly good.

[Kweassa]

A question, Tilt.

 The quote Hohun dug up:

Early La5 fns were fitted with only 3 of the 5 tanks fitted in the original La 5 this infact reduced range to circa 500Km..... with the advent of the metal sparred La5FN they introduced 4 tank set ups (2 x 168 L & 2 x 148 L) totalling 632 L . Air intake clutter at the wing roots and attempts to lighten the fuel load forced the La 7 back to 3 tanks ( 460/470 L).

 seems to contradict what you have written in your own La-5FN site(http://www.btinternet.com/~fulltilt/deshist.html#La-5FN) where it states:

However through out 1943 and 1944 the La-5 FN benefited from a continued weight saving program as certain wooden parts were replaced with light alloy parts. The fuel tanks were later changed to a 4 tank set ( when the metal sparred wings were adopted) but this did not add to the aircrafts range which had been reduced by the heavier breathing engine. Combat mission flight duration at full power was now only 40 minutes, however this could be extended to 2 hours and 32 minutes when at reduced engine revs of 1600rpm.

 So am I missing something here? Got me confused

[Tilt]

Originally posted by Kweassa


 So am I missing something here? Got me confused

No Kweassa I think I am.

I need to check my notes but the range comparison is with that of the earlier 5 tank la5f and my site did not make that clear.

Basically Lavochkin was under continued pressure to bring range back to that of the earlier type.

Very little data (ie next to none) is available to me regarding the 4 tank set.

Its possible that Gorky never produced such a 4 tank la5Fn and it was done at either Moscow or more likly somewhere like Tblisi (Georgia) which was a small, comparatively well resourced but initially inexperienced plant (it later produced the bulk of the 3 cannon la7's that saw service) This is just speculation.

I would speculate with some confidence that the 4 tank la5fn was a rare beast as it was almost certainly not produced at Gorky and if produced at Moscow would have stopped as soon as La7 production kicked in. Again note this is speculation.

[niklas]

Originally posted by Tilt

and we still have a 50kg wheel base mis balance.

edited: misunderstood question

Donīt forget that a weigth difference on the outside of the wing can produce a larger difference on the wheels. Itīs momentum question. additional 10kg on the outside of a wing can give you easily this difference. Radio mounted offside. Speed indicator tube etc.

niklas

[Kweassa]

Thanks for the answer, Tilt. But I have some more questions popping up my head

 So, from what I learned from this excellent thread(and assume ), the differences in the early models of the La-5FN and the latter model is as follows:


1) early La-5FNs had their WEP limited, while later models, due to better cowling design and construction process, had their WEP effectivity and longetivity increased.

2) early La-5FNs had 3 fuel tanks, while later models had four, accompanying the change to metallic wings.

3) Due to the difference in fuel tank number, the early La-5FN had a flight range circa. 500km, while the later versions had more than 600km.

 Can the above sum it up adequately?

 I also have some serious of smaller questions, in that case.

1) Is the increase in WEP performance, purely from the cowling design alone?

2) I know you've stated it once, but it seems the difference in performance is never really clarified, between the earlier and later La-5FNs. Is there any documental proof referring that there was a difference in performance between the two?

3) With the promise that I'm not gonna hold the numbers to you, nor will I comment it elsewhere lightly without your permission , if there isn't a really clear indication of difference in performance documented on paper, what would your expectation of the differing performance be, between the early and later models? Especially considering the speed performance at sea level and maximum speed at altitude?

4) What would be the first thing you'd look at, if you see a La-5FN externally, internally and performance wise, without documented tecbnical data on paper, that you could use to differentiate the earlier version and the latter?

 To tell you the truth, I'm into a small discussion with a group of people about the La-5FN modelled in IL-2/FB. It's not one of those "big" discussions in UBI forums or something, just a small disagreement around my squad mates who are all Koreans, and in our small, private forum.

 I'm convinced that the La-5FN modelled in FB is that of 1944, on the grounds of performance(which closely matches our AH La-5FN), WEP duration, and listed range in the object viewer. If there was a typical simulated plane as in the games we play(thus, we have info on speed/climb performance, internal cockpit modelling, exterior 3D modelling, but no official confirmation from the developers), what would be the major points to verify that La-5FN's date of service?  

 Also, if you have tried FB, or have any data on the La-5FN modelled there, I'd really appreciate it if you gave your expert opinion I'd also appreciate any other input.. Hohun? Niklas? Anyone ??

[Tilt]

Originally posted by Kweassa
Thanks for the answer, Tilt. But I have some more questions popping up my head

 So, from what I learned from this excellent thread(and assume ), the differences in the early models of the La-5FN and the latter model is as follows:


1) early La-5FNs had their WEP limited, while later models, due to better cowling design and construction process, had their WEP effectivity and longetivity increased.

My view. I have more data indicating(suggesting) that the la5fn had engine temperature management issues that limited the wep duration than i have data that actually confirms that WEP @2500 was as available on the la5Fn as it was on the La7.

If we are to accept this then it is for all La5fn's as it is a function of cowling and air flow design around the engine that was never modified on the La5fn.

The problem is that hard data pertaining only to the La5fn is hard to find in abundance. Rechlin suggests it. Czech pilots flying in 44 mentioned it. I have one set of Russian curves (which were originally produced for a magazine article) that state it. I would love some VVS test results that confirm it.

Hence if asked an opinion I would sugest that the la5fn did not have access to the length of wep duration the la7 had. If you ask me for fact then I hesitate.

2) early La-5FNs had 3 fuel tanks, while later models had four, accompanying the change to metallic wings.

i think the correct statement would be that some late 43/early44 models had the 4 tank set. The bulk of the La5Fn's would have had the 3 tank set even those produced at Gorky till Oct 44.

3) Due to the difference in fuel tank number, the early La-5FN had a flight range circa. 500km, while the later versions had more than 600km.

Again its better not to draw a line in time to say before this date 3 tanks and after this date 4 tanks. However it seems that the 4 tank La5fn had the same range as the 5 tank la5f.... i will check the actual range when I get home but think "more than 600" to be a safe phrase.

 
1) Is the increase in WEP performance, purely from the cowling design alone?

la7 exhaust tubes were re routed to improve air flow between the rear cylinders.

La7 spinner was shaped to improve air flow into the forward engine chamber.

La7 upper cylinder engine air flow was not displaced by the supercharger intake duct dropping behind the rear upper cylinders like the La5fn. Both had to accomadate the cannon barrels however.

re cowling

La5fn cowling had more hinge points and was not as close fitting as the La7. La5fn cowling was not a full 360 degree affair with air loss to the bottom where it profiled the oil cooler. further it was not a perfect cylinder when properly fitted (it had a bulged middle) hence good fit and seal was difficult along the hinge and join lines.


2) I know you've stated it once, but it seems the difference in performance is never really clarified, between the earlier and later La-5FNs. Is there any documental proof referring that there was a difference in performance between the two?

Yes there is. It is expressed in terms of "x" kilometers/hour below those figures gained from development model. I will dig them up for you. Basically the history shows that initial production machines were significantly below what was expected and this was latterly corrected.

3) With the promise that I'm not gonna hold the numbers to you, nor will I comment it elsewhere lightly without your permission , if there isn't a really clear indication of difference in performance documented on paper, what would your expectation of the differing performance be, between the early and later models? Especially considering the speed performance at sea level and maximum speed at altitude?

see above

4) What would be the first thing you'd look at, if you see a La-5FN externally, internally and performance wise, without documented tecbnical data on paper, that you could use to differentiate the earlier version and the latter?

virtually no external indicators unless you had the production number and could place it close to some published  AC with known production numbers and date of production.

A few ac from the first batch may have some clues from the type of radio mast used (vertical or forward leaning) forward leaning being the std adopted.

The use of a small cockpit air inlet forward and below the front screen would suggest it is not one of the first batch (but this could have been retro fitted.)

If it is carrying the Fn rhomboid insignia then it is not from the 1st batch. Some of which even had the old la5f circular insignia still on them.

But these last three indicators identify a (comparatively)small group of AC rushed out of production in early 43 to put in the front line around Kursk. I say comparatively because when production was put into full swing at Gorky this one plant alone was producing several hundred a month by October 43.

What would be the major points to verify that La-5FN's date of service?  

Unfortunately I would say its all up weight and performance would be the best indicators. (the very things you would wish to cross reference). Fuel tanks aside the la5fn got marginally lighter as it was developed on a production basis. This is really the adoption of lighter metal components in place of wood. The all metal spar being a significant improvement.

The next problem is slotting these developments into the best time frame. Its fairly safe to say the La5fn optimum was achieved by early 44. However we have to understand that components were never discarded......production was king. If you had 1000 wings of an older design they were used regardless of the benefits of the newer wings now in production at another plant.

Hence you could argue that eg Moscow plant had optimised performance by Nov 43 (with a metal spar even) whilst Gorky never had the advantage of  the lighter wing even when it ceased production in Oct 44. So which model do you adopt for your  FM? As Gorky was the biggest producer by far this would be the safe bet and Gorky was able to continue lightening the AC (in other areas) even after Moscow had wholly switched production to la7's by May/June 44. So it does not mean that Gorky produced AC were held to a 43 standard in all aspects.

To grasp this understanding further you have to step out of the "western" view of ac production and into a GPW Russian one.

The Lavochkins and Yaks were produced in a regime that considered the life expectancy of such fighter aircraft to be of just a few months (between 3 and 5). Hence we see what are actually "throw away" aircraft being produced in significant numbers under massive production pressure from the State.

I am sure that somewhere in Russia now are some original VVS test figures which Maddox may have had access to. The problem with all such data is that as soon as Maddox or HTC show their sources they open them up to copying by competitors or a level of critique from their players (and competitors) that is avoided by a higher level of confidentiality. Its obvious to me that there is a certain amount of "filling in the blanks" with some AC FM's where data is missing. I am usually very impressed to see how well the blanks are filled when the data is laterly discovered.

[Kweassa]

Thank you for the detailed response! It's helping me understand the plane smuch better.  I appreciate the effort and time you put into the answers, and also thank you advance for the "numbers digging"!!

[Tilt]

It seems there is a way to date the \la5Fn if you can see the radio wires.

Early units used the same wire pattern as the la5f with two wires from the top of the tail post one of which went to the bottom of the mast the other to the top.

The bulk of the production units had both wires  from the tail post leading and joining at the top of the mast with an extra wire dropping to a fuselage spigot. As per early La7's.

Very late production units had this last extra wire dropping to a spigot on the rear cockpit glass. This is post la7 commencing production so would be Gorky units from June 44 onwards.

other notes

Forget my reference to tblisi it only made a few la5FN's in 43 (5). I need to cross reference some other stuff before confirming it.